Southeastern Atlantic Canada, Northwestern Africa, and Continental Drift

1971 ◽  
Vol 8 (10) ◽  
pp. 1218-1251 ◽  
Author(s):  
Paul E. Schenk
Keyword(s):  
North Atlantic ◽  
Plate Tectonics ◽  
Continental Drift ◽  
Continental Collision ◽  
Atlantic Canada ◽  
Island Arcs ◽  
Late Precambrian ◽  
The North ◽  
Northwestern Africa ◽  
Southeastern Atlantic

The model applies plate-tectonics to explain the geologic evolution of southeastern Atlantic Canada and northwestern Africa. The North Atlantic may have opened and closed several times from the middle Cryptozoic to the present. Closings of the ocean caused collisions between continents and also island arcs. Openings were ragged so that parts of one continent were transposed to the other, and sialic fragments became offshore micro-continents. Africa has progressively lost increments of continental crust to North America.Precambrian blocks of southeastern Atlantic Canada may be remnants of an African shelf. which was crumpled during a billion-year old continental collision (Grenville orogeny). After ragged rifting during the Late Precambrian these fragmentary blocks were carried eastward as micro-continents off Africa. Both early (Danakil Alps of the Red Sea) and late-stage (Canary Islands) recent analogues appear valid. The micro-continents ponded turbidites, which formed rise-complexes off Africa. Continental glaciations in the Late Precambrian and Late Ordovician not only make excellent inter-regional chronostratigraphic units in almost unfossiliferous strata. but also may confirm the African origin of Nova Scotia. Subducting plate-margins increased offshore volcanism and narrowed the Paleozoic Atlantic. Late Paleozoic continental collision again between Africa and North America sandwiched the micro-continent, telescoped the sedimentary/volcanic complexes, and flooded the sutured area with granodiorite. Middle Carboniferous carbonates and sulfates record vestiges of the Paleozoic Atlantic, and mixing of the Euro-African fauna with that of the western Paleozoic Atlantic of the northwestern Appalachians. The Atlantic was closed at least along the latitude of Atlantic Canada and Morocco. During the Mesozoic, an accreting margin uplifted this area, quickened redbed deposition and volcanism, initiated restricted marine sedimentation, and inaugurated the present North Atlantic east of the African remnant of southeastern Atlantic Canada.

Southeastern Atlantic Canada, Northwestern Africa, and Continental Drift: Discussion

1973 ◽  
Vol 10 (4) ◽  
pp. 584-586 ◽  
Author(s):  
H. Hollard ◽  
J. P. Schaer
Keyword(s):  
Continental Drift ◽  
Atlantic Canada ◽  
Northwestern Africa ◽  
Southeastern Atlantic

Southeastern Atlantic Canada, Northwestern Africa, and Continental Drifts: Reply

1973 ◽  
Vol 10 (4) ◽  
pp. 586-588
Author(s):  
Paul E. Schenk
Keyword(s):  
Atlantic Canada ◽  
Northwestern Africa ◽  
Southeastern Atlantic

scholarly journals Archaean Plate Tectonics in the North Atlantic Craton of West Greenland Revealed by Well-Exposed Horizontal Crustal Tectonics, Island Arcs and Tonalite-Trondhjemite-Granodiorite Complexes

2020 ◽  
Vol 8 ◽  
Author(s):  
Adam Andreas Garde ◽  
Brian Frederick Windley ◽  
Thomas Find Kokfelt ◽  
Nynke Keulen
Keyword(s):  
North Atlantic ◽  
Plate Tectonics ◽  
Plate Tectonic ◽  
Island Arcs ◽  
West Greenland ◽  
Structural Style ◽  
Modern Style ◽  
Greenstone Belts ◽  
Lower Crustal ◽  
North Atlantic Craton

The 700 km-long North Atlantic Craton (NAC) in West Greenland is arguably the best exposed and most continuous section of Eo-to Neoarchaean crust on Earth. This allows a close and essential correlation between geochemical and isotopic data and primary, well-defined and well-studied geological relationships. The NAC is therefore an excellent and unsurpassed stage for the ongoing controversial discussion about uniformitarian versus non-uniformitarian crustal evolution in the Archaean. The latest research on the geochemistry, structural style, and Hf isotope geochemistry of tonalite-trondhjemite-granodiorite (TTG) complexes and their intercalated mafic to intermediate volcanic belts strongly supports previous conclusions that the NAC formed by modern-style plate tectonic processes with slab melting of wet basaltic oceanic crust in island arcs and active continental margins. New studies of the lateral tectonic convergence and collision between juvenile belts in the NAC corroborate this interpretation. Nevertheless, it has repeatedly been hypothesised that the Earth’s crust did not develop by modern-style, subhorizontal plate tectonics before 3.0 Ga, but by vertical processes such as crustal sinking and sagduction, and granitic diapirism with associated dome-and-keel structures. Many of these models are based on supposed inverted crustal density relations, with upper Archaean crust dominated by heavy mafic ridge-lavas and island arcs, and lower Archaean crust mostly consisting of felsic, supposedly buoyant TTGs. Some of them stem from older investigations of upper-crustal Archaean greenstone belts particularly in the Dharwar craton, the Slave and Superior provinces and the Barberton belt. These interpreted interactions between these upper and lower crustal rocks are based on the apparent down-dragged greenstone belts that wrap around diapiric granites. However, in the lower crustal section of the NAC, there is no evidence of any low-density granitic diapirs or heavy, downsagged or sagducted greenstone belts. Instead, the NAC contains well-exposed belts of upper crustal, arc-dominant greenstone belts imbricated and intercalated by well-defined thrusts with the protoliths of the now high-grade TTG gneisses, followed by crustal shortening mainly by folding. This shows us that the upper and lower Archaean crustal components did not interact by vertical diapirism, but by subhorizontal inter-thrusting and folding in an ambient, mainly convergent plate tectonic regime.

Geochronology and continental drift—the North Atlantic

1965 ◽  
Vol 258 (1088) ◽  
pp. 180-191 ◽  
Keyword(s):  
North Atlantic ◽  
East Coast ◽  
Continental Drift ◽  
Oceanic Islands ◽  
Northern Europe ◽  
Mean Square ◽  
The West ◽  
The North ◽  
The North Atlantic ◽  
Centre Of Rotation

A geometrical fit of the land masses of northern Europe, Canada and Greenland has been constructed by Dr A. G. Smith using the method devised by Sir Edward Bullard and M r J. E. Everett. The method involves taking points of latitude and longitude on the 500 fm. line at intervals of about 30 miles along the two coasts to be fitted. Young features such as oceanic islands are ignored. By a method of successive approximation, the computer ‘homes in ’ on to the centre of rotation which gives the minimum root mean square misfit between the rotated coastlines j the misfit being measured as the discrepancy of longitude relative to the centre of rotation. In this manner the 500 fm. line along the east coast of Greenland has been fitted to that of northwestern Europe to form one unit. This unit, that is, the 500 fm. line of the west coast of Greenland and the Channel approaches have been fitted on to the 500 fm. line of Canada. Maps of this fit drawn as a conical projection with two standard parallels of latitude will be presented and will show the geochronological patterns across the reconstructed land masses.

The growth of the North Atlantic Ocean by the spreading of its floor

Polar Record ◽  
1967 ◽  
Vol 13 (86) ◽  
pp. 579-588 ◽  
Author(s):  
P. F. Friend
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Continental Drift ◽  
Reasonable Doubt ◽  
The North ◽  
Northern Atlantic ◽  
The North Atlantic ◽  
Northern Atlantic Ocean

Argument about whether or not continental drift has occurred has been continuous and inconclusive since drift was first advocated fifty years ago by scientists from a number of different disciplines. Recently, evidence has accumulated to establish beyond reasonable doubt that this drift has indeed occurred. In this paper I discuss some features of the drift, particularly those concerning the northern Atlantic Ocean. The investigations of geologists should now be turned from the question of whether drift has occurred, to the manner in which it has occurred.

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